An apparatus of the type described is illustrated, for example, in the commonly owned German Patent 37 12 828 and German Open Application DE-OS 40 24 994 A1. In both of these systems, a funnel is provided which can be rotated about the axis of the frustocone, which axis forms an acute angle with the axis of the conveyor screw lying along the wall of the funnel and forcing the mass into a passage communicating with an injection molding machine or extruder unit.
In terms of prior art, mention can also be made of German Patent Document 137 813 which describes a meat chopper having a worm whose flight is interrupted to cooperate with pins projecting toward the worm in the regions of such interruption. The interaction of the worm and the pins serves to comminute the meat. A screw vent is described in U.S. Pat. No. 4,117,548 which has a pin extending into a region in which a flight is interrupted and in German Published Application DE-AS 1 003 947, the cross section of an extruder worm is serrated or fluted to promote the shearing action. Finally, mention may be made of DE-AS 1 529 803 which provides a pocket in the worm chamber of an extruder also to cooperate with the worm in the advance of the flowable mass therealong.
However, in systems of the type described in German Patent DE 37 12 828 and DE-OS 40 24 994, in which the wall of the frustoconical funnel is relatively smooth and, as is customary, may be chromium coated to reduce wear, with long operating intervals with materials which are relatively abrasive, for example, recycled plastics, fillers, glass fibers, ceramics and the like, the materials processed additionally smooth and polish the inner surface so that it tends to lose all of its original surface roughness.
As a consequence, material can slip past the feeder conveyor so that the conveyor, while continuously operating, does not continuously feed the mass and hence the output of the apparatus is reduced.
When an attempt was made to solve this problem by providing worms or screws with teeth, the improvement was minimal.